U.S. Pat. No. 5,572,228 issued Nov. 5, 1996 and U.S. Pat. No. 5,815,124 issued Sep. 29, 1998 describe evanescent coupling antennas which employ rotatable cylinders placed in close proximity to a dielectric rod waveguide and operative to radiate the coupled energy in directions determined by the period of features on the surface of the cylinder. By defining rows of features where the features of each row have a different period, the radiation can be directed in a plane over a range determined by the different periods and by rotating the cylinder about an axis parallel to the axis of the waveguide.
The features on the cylinder surface, of each of the antennas disclosed in the above-noted patents, comprise conductor strips of like thickness and at a given and different spacing in each row about the cylinder. The operation of such an antenna as well as the advantages in such applications as vehicle collision avoidance systems for automobiles and aircraft and the like are described in the above-noted patents which are incorporated herein by reference.